When I try to change a file name that starts with '04' and japanese chars, thunar dies from a segmentation fault, but the filename does change. I've been running thunar as root when this happens, if that matters.
I've now had the same problem with files starting with '01' and '12', which makes me think it's probably related to certain characters, rather than the starting number.
Can you retry with Thunar 1.6.11 which fix lots of renaming bugs ?
I cannot reproduce with Thunar 1.8.1, probably fixed since then, reopen if not.